1. Field of the Invention
The present invention relates to a reproduction apparatus, in particular, processing for reproducing information data encoded using multiple different encoding systems.
2. Related Background Art
In recent years, more and more devices having a function of recording and reproducing moving images and audio onto and from a memory card have become available.
For instance, although digital cameras formerly had only a function of recording and reproducing still images, many digital cameras also having a function of recording and reproducing moving images and audio have currently been loaded.
Also, in the field of video cameras, apparatuses having a function of recording and reproducing moving image data onto and from not only a tape medium but also a disk medium, such as a memory card, an optical disk, or a hard disk (HDD), have come into being. Further, video cameras that record and reproduce image data and audio data onto and from a memory card or a disk medium instead of a tape medium have also come into being.
Ordinarily, when digital video image/audio data is recorded into a memory card or a disk medium in this manner, a data amount reduction is achieved through encoding of the data to be recorded.
Commonly used moving-image compression encoding system standards include standards stipulated by Moving Picture Experts Group (MPEG), such as MPEG2 and MPEG4, each of which also defines an audio-data encoding system. Also, there are various audio-data compression systems such as G.726, Advanced Multi Rate CODEC (AMR), and Advanced Audio Coding (AAC) recommended by International Telecommunications Union (ITU).
Generally, irreversible compression is performed in those compression systems and it is possible to achieve a data amount reduction through encoding processing, but the image quality and audio quality of encoded data are deteriorated from those of original data.
Also, generally, as data is compressed at a higher compression ratio, the image quality and audio quality of encoded data are lowered. However, the degree of the lowering of the image quality and audio quality also greatly depends on the performance of a compression algorithm itself and compression encoding systems with less degradation are currently under loadment and standardization.
As described above, currently, multiple kinds of encoding systems are widely used, so a situation is conceivable in which moving image data and audio data compression-encoded and recorded using multiple kinds of encoding systems are coexistently recorded in one memory card or disk medium.
Therefore, it is desired that it is possible to reproduce data compressed using various kinds of encoding systems with one reproduction apparatus.
The amount of computation in decoding processing performed at the time of reproduction of compressed moving image data is large, so a dedicated hardware is used in many cases expect for an environment, such as a personal computer, in which there exist sufficient resources such as a CPU and a memory.
On the other hand, the processing amount of expansion and decoding processing of compressed audio data is smaller than that of moving image data, so in the case of a built-in device whose hardware resources are limited, the processing is achieved by software in many cases. When the processing is achieved by software, a compression program and an expansion program are collectively referred to as a “codec” (COder DECoder).
In Japanese Patent Application Laid-open No. 2001-202094, a reproduction apparatus is proposed which reproduces audio data encoded using multiple compression encoding systems, where a codec is loaded into a work RAM from a codec storing memory or an external device on a network in accordance with the encoding system of a file to be reproduced and then is executed.
According to Japanese Patent Application Laid-open No. 2001-202094, it becomes possible to reproduce even a reproduction target encoded using an encoding system, which requires a decoding program that is not stored in an internal memory of the apparatus, by loading the decoding program from the outside.
When doing so, in Japanese Patent Application Laid-open No. 2001-202094, after audio data that should be reproduced is designated, a codec program corresponding to the encoding system of the audio data is loaded into the RAM.
However, a long time is taken to load a decoding program into the RAM, which leads to a problem that it is impossible to start reproduction promptly after issuance of a reproduction-start instruction by a user.
Also, generally, a built-in device is greatly limited in hardware resources and it is impossible to concurrently load multiple decoding programs into a RAM in many cases. In such a case, there arises a necessity to load decoding programs stored in a flash ROM into the RAM, which leads to a problem that it is impossible to start reproduction before the loading of the decoding programs into the RAM is completed.